1. Field of the Invention
The invention relates to processes for anionic polymerization of acrylic and/or methacrylic acid derivatives or their ammonium salts and/or acrylonitrile or methacrylonitrile or their derivatives.
2. Description of the Related Art
The anionic polymerization of vinyl monomers has the advantage, relative to the process for radical polymerization, that polymers with a much more limited molecular weight distribution are obtainable and that block polymerizations can be performed in a comparatively simple way (see, e.g., U.S. Pat. Nos. 4,351,924, 4,414,372, EP-A-0 145 263, Macromonomers 17 (1984) pages 1415-1417and Angew. Chem. [Appl. Chem.] 100 (1988) pages 1026-1030).
While monomers such as styrene enter into quite smooth anionic polymerizations, difficulties arise with monomers such as acrylates and methacrylates, since the increasing or anionic chain ends can enter into undesired secondary reactions, such as intramolecular Claisen reactions, which results in stopping the polymerization. Therefore, low temperature (e.g., -30.degree. to -78.degree. C.) are necessary and the reaction must include organo-metallic initiators, which are complex and expensive.
In the case of group transfer polymerization, the reaction can be performed at room temperature with the formation of polyacrylates and polymethacrylates with limited molecular weight distribution. However, the initiators and the catalysts, which are necessary, are expensive compounds (see, e.g., U.S. Pat. No. 4,414,372, 4,417,034, EP-A-0 145 283, Macromonomers 17, (1984) 1415-1417, Angew. Chem. [Appl. Chem.] 98 (1986) 1116-1118 and Angew. Chem. 100 (1988) 1026-1030). The use of tetraalkylammonium salts of resonance-stabilized carbanions as initiators has the advantage of producing polyacrylates and polymethacrylates with limited molecular weight distribution can be produced at room temperature without catalysts. (Angew. Chem. 100 (1988) 1422-1423, West Germany Laid Open No. 3727528, Europe Laid Open No. 306714, Japan Laid Open No. 1069605). But the number of easily accessible carbanions of this type is limited. It is, also, difficult, if not impossible, to incorporate certain functionalities, such as heterocycles or amino groups, in the initiator. This is important also with respect to the production of polymers with reactive or potentially reactive functional groups on a chain end.
Therefore, a process is needed for anionic polymerization of acrylic and/or methacrylic acid derivatives or their ammonium salts which is simple and inexpensive to use.